Re: (ET) Nope, that wasn't it...

[Michael J DeLiso <mjdeliso juno com>]

Chris,
Two of the list of things that kill brushes, are water and oil.
If the armature laminations are rusted it was water, makes them swell,
cuts right into the 
wiring. The moisture is a normal result of putting the mower away hot or
cleaning it with a garden hose.
As it cools it sucks the water into the motor case.
Also attacks the magnets, they swell and crack. 
Oil damage would be all over the brush holders, probably from the top
bearing. 
The new brushes I have are 7/8 inch long. Not as smeary as the old ones.
The white metal, the copper leads, that plastic that the brush holders
are made of, makes a
good soup for corrosion.
I sealed the last mower motors I rebuilt  with paint and silicone RTV.
Time will tell if it was a smart decision.

Mike D

On Thu, 08 Apr 2004 22:21:53 -0400 Chris Zach <czach computer org>
writes:
> *nod* Given that the thermo switch is protecting the motors, my guess 
> is 
> the brushes swelled and stuck when I applied full power to the motor 
> by 
> bypassing the breaker.
> 
> Which makes the root question: "What caused this" even more of a 
> mystery. What would cause an armature to short simply by sitting in 
> a shed?
> 
> Chris
> 
> 
> RJ Kanary wrote:
> 
> >    Sounds like time to go to an auto- electric shop that has a 
> growler, and
> > find out if the armatures are dead. You could have a chicken/ egg 
> situation
> > here.
> >     Did the brushes stick in the guides because of excessive 
> current draw
> > due to shorted windings , or was the commutator overheated and 
> damaged due
> > to poor brush contact, due to the scenario that I have observed, 
> mentioned
> > in my previous post ?
> >